An example of DRAMs capable of shrinking the area of word-line driver circuitry by use of P-channel MOSFETs of the so-called ring type is disclosed in U.S. Pat. No. 6,236,258B1. In addition, an example that employs ring-shaped gate electrodes to accomplish breakdown voltage enhancement is found in JP-A-10-050957.
In the devices as taught by the above-identified Japanese patent documents, each is such that the ring-shaped gate MOSFETs are applied to word drivers and sub-word drivers. These documents fail to teach or suggest guidelines as to the sizes of the ring-shaped gates and methodology for reducing deviations of parasitic resistance components. More principally, the documents are completely silent about exact applicability to CMOS technologies. In short, the ring-shaped gates as taught thereby are mere examples to be applied only to N-channel MOSFETs or P-channel MOSFETs. CMOS devices are the ones that make up a circuit by using an N-channel MOSFET and a P-channel MOSFET as a pair. In this respect, it becomes important to provide efficient layout while at the same time maintaining the circuit relationship of the both.